1. Field of the Disclosure
This disclosure relates generally to drilling motors and progressive cavity pumps for use in wellbore operations.
2. Brief Description of the Related Art
To obtain hydrocarbons such as oil and gas, boreholes or wellbores are drilled by rotating a drill bit attached to a drill string end. A substantial proportion of current drilling activity involves drilling deviated and horizontal boreholes to increase the hydrocarbon production and/or to withdraw additional hydrocarbons from the earth's formations. Modern directional drilling systems generally employ a drill string having a drill bit at the bottom that is rotated by a positive displacement motor (commonly referred to as a “mud motor” or a “drilling motor”). A typical mud motor includes a power section that contains a stator and a rotor disposed in the stator. The stator typically includes a metal housing lined inside with a helically contoured or lobed elastomeric material. The rotor includes helically contoured lobes made from a metal, such as steel. Pressurized drilling fluid (commonly known as the “mud” or “drilling fluid”) is pumped into a progressive cavity formed between the rotor and stator lobes. The force of the pressurized fluid pumped into the cavity causes the rotor to turn in a planetary-type motion. The elastomeric stator liner provides seal between the stator lobes and rotor lobes. The elastomeric liner also provides support for the rotor and thus remains under high load conditions during operation of the mud motor or the pump. Each lobe includes a load side and a sealing side. The load side is typically under much greater stress and strain compared to the sealing side. The currently available drilling motors employ symmetrical geometry for the rotor lobes and for the inner contour of the stator. Such symmetrical designs do not take into the effects of the load conditions on the stator and rotor lobes.
There is a trade-off between reduced stress and strain on the uniform liner and the preservation of the volumetric efficiency and power output of the drilling motor.
The disclosure herein provides drilling motors and progressive cavity pumps with asymmetric lobe geometries for rotor and/or stators that address some of the deficiencies of symmetrical lobe geometries.